Eversion resistant sleeves

ABSTRACT

The invention relates to improved means for preventing eversion and subsequent obstruction of thin-walled, floppy gastrointestinal liners implanted in the digestive tract of an animal. The implantable devices include an anchor adapted for attachment within a natural body lumen and a thin-walled, floppy sleeve open at both ends and defining a lumen therebetween. A substantial length of the sleeve has material characteristics that result in the sleeve being prone to eversion in the presence of retrograde pressures. Exemplary eversion-resistant features provide an increased stiffness and/or an increased friction coefficient between the anchor and the proximal end of the sleeve to resist eversion. In some embodiments, the eversion-resistant feature includes an anti-buckling element, such as a wire coupled along the substantial length of the sleeve.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/147,984, filed Jun. 8, 2005 now U.S. Pat. No. 7,766,973, which claimsthe benefit of U.S. Provisional Application Nos. 60/645,296 filed onJan. 19, 2005 and 60/662,570 filed on Mar. 17, 2005.

The entire teachings of the above applications are incorporated hereinby reference.

BACKGROUND OF THE INVENTION

According to the Center for Disease Control (CDC), over sixty percent ofthe United States population is overweight, and almost twenty percentare obese, presenting an overwhelming health problem. Moreover,obesity-related conditions cause as many as 280,000 deaths per year,generate $51 billion in annual US healthcare costs, and cause Americansto spend $33 billion per year on weight loss products. For example, oneof the principle costs to the healthcare system stems from theco-morbidities associated with obesity. Type-2 diabetes has climbed to7.3% of the population. Of those persons with Type-2 diabetes, almosthalf are clinically obese, and two thirds are approaching obese. Otherco-morbidities include hypertension, coronary artery disease,hypercholesteremia, sleep apnea and pulmonary hypertension.

Two surgical procedures commonly performed that successfully producelong-term weight loss are the Roux-en-Y gastric bypass and thebiliopancreatic diversion with duodenal switch (BPD). Both proceduresreduce the size of the stomach plus shorten the effective-length ofintestine available for nutrient absorption. However, these are serioussurgical procedures with significant side effects, and thus they arereserved for the most morbidly obese.

Other devices to reduce absorption in the small intestines have beenproposed (See U.S. Pat. No. 5,820,584 (Crabb), U.S. Pat. No. 5,306,300(Berry) and U.S. Pat. No. 4,315,509 (Smit)). However, these devices areyet to be successfully implemented.

Examples of gastrointestinal sleeves have been described, which havegreat promise for treating obesity while minimizing the risks of surgery(See, for example, Meade et al., U.S. Utility application Ser. No.10/858,851, filed Jun. 1, 2004; the entire teachings of which areincorporated herein by reference). It is important in any intestinalsleeve application to maintain patency of the device. When a sleeve issubjected to retrograde pressure, the sleeve may tend to evert (i.e.,fold inward upon itself). Such eversions are undesirable and may lead toblockage, sleeve damage, and related complications. Thus, furtherimprovements are desired to more fully realize the advantages which canbe provided by gastrointestinal sleeves while minimizing any risk ofcomplications.

SUMMARY OF THE INVENTION

There is a need for liners implantable within natural body lumens of ananimal body. Moreover, there is a need for implantable sleeves that arethin-walled and floppy, yet resistant to eversion.

This invention relates to improved methods and devices for preventingeversion and subsequent obstruction of a thin-walled, floppy sleeveimplant, anchored within a natural lumen of an animal body. The devicemay include an anchor adapted for attachment within a natural body lumenand a thin-walled, floppy sleeve open at both ends and defining a lumentherebetween. A substantial length of the sleeve material has one ormore characteristics that result in the sleeve being prone to eversion.Such characteristics include thinness, floppiness and a low frictioncoefficient.

A particular application is anchoring gastrointestinal liners within thesmall intestine of an animal body. In some embodiments, the deviceincludes an eversion-resistant feature disposed between the anchor andthe proximal end of the sleeve adapted to inhibit eversion of the sleevein the presence of retrograde pressures. The eversion-resistant featuremay provide an increased stiffness relative to the sleeve's stiffness.Some ways of increasing stiffness include providing a different materialthat is stiffer than the sleeve itself. Alternatively, or in addition,the stiffness can be increased by providing an increased wall thicknessrelative to that of the sleeve. For example, thicker walls can be formedby using more than one layer of material (i.e., multiple layers of thesleeve material). Alternatively, or in addition, stiffness can beincreased by providing a reinforcing member. For example, one or moresoft, flexible wires can be coupled to the proximal end of the sleeveadjacent to the anchor.

In some embodiments, a surface of the eversion-resistant featureprovides an increased coefficient-of-friction relative to that providedby the surface of the floppy sleeve itself. For example, the increasedcoefficient of friction can be provided using a different material thanthe sleeve. The different material may include a coating applied to asurface of the device. Alternatively or in addition, the increasedcoefficient of friction can be provided by texturing at least a portionof a surface of the sleeve. In either instance, the surface may be theinterior surface, the exterior surface, or both the interior andexterior surfaces.

To inhibit eccentric eversions, the device may include a centeringelement adapted to focus collapse of the device just distal to theanchor towards the longitudinal axis of the anchor. For example, thecentering element can include a sacrificial proximal portion, referredto as a “crumple zone” coupled to a distal reinforcing portion. Thecrumple zone is adapted to collapse in the presence of retrogradepressures before any substantial collapse of the reinforcing element.

Alternatively or in addition, the crumple zone can include a taperedsegment, such as a tapered cone. The tapered segment defines a proximalopening having a first diameter and a distal opening having a seconddiameter that is less than the first. Retrograde pressures tend to movethe distal opening proximally while tapering inhibits lateral movementtowards the walls of the body lumen. Preferably, the eversion-resistantelement is adapted to partially collapse upon itself thereby forming avalve allowing flow in an antegrade direction, while prohibiting flow ina retrograde direction, the valve enhancing the eversion-resistanceperformance of the sleeve.

The invention also relates to methods and devices that include an anchoradapted for attachment within a natural body lumen and a thin-walled,floppy sleeve open at both ends and defining a lumen therebetween. Asubstantial length of the sleeve has material characteristics thatresult in the sleeve being prone to eversion. The device also includesan eversion-resistant feature disposed along a substantial length of thesleeve adapted to inhibit eversion of the sleeve in the presence ofretrograde pressures. In some embodiments, the eversion-resistantfeature includes an anti-buckling member providing increased stiffnessalong the length of the sleeve. For example, the anti-buckling membercan be a wire coupled along the length of the sleeve.

The invention also relates to methods and devices that include a floppysleeve open at both ends defining a lumen therebetween and an anchoradapted for attaching at least a proximal portion of the sleeve withinthe small intestine of an animal body. A substantial length of thesleeve has material characteristics that result in the sleeve beingprone to eversion. The device also includes an eversion-resistantfeature. In some embodiments the eversion-resistant feature is disposedalong a substantial length of the sleeve and is adapted to inhibiteversion of the sleeve in the presence of retrograde pressures. Forexample, the eversion-resistant feature may include an anti-bucklingmember, such as a wire, providing increased stiffness along the lengthof the sleeve. In other embodiments, the eversion-resistant feature isdisposed between the anchor and a proximal length of the thin-walled,floppy sleeve.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1A is a cross-sectional diagram of an implantable anchored sleeve;

FIG. 1B is a cross-sectional diagram of the implantable anchored sleeveof FIG. 1A in a concentrically-everted state;

FIG. 1C is a cross-sectional diagram of the implantable anchored sleeveof FIG. 1A in a eccentrically-everted state;

FIGS. 2A and 2B are schematic diagrams of an implantable anchored sleeveaccording to one embodiment of the invention;

FIG. 3A is schematic diagram of an eversion pressure measurement testsetup;

FIG. 3B is schematic diagram of an alternative eversion pressuremeasurement test setup;

FIGS. 4A and 4B are schematic diagrams of an exemplary implantableanchored sleeve according to one embodiment of the invention having atapered section;

FIGS. 5A and 5B are schematic diagrams of an exemplary implantableanchored sleeve according to one embodiment of the invention having aneccentric-eversion resistant feature;

FIGS. 6A and 6B are schematic diagrams of an exemplary implantableanchored sleeve according to one embodiment of the invention having atapered section and an eccentric-eversion resistant feature;

FIGS. 7A and 7B are schematic diagrams of an eccentric eversionmeasurement test setup;

FIG. 8 is schematic diagram of an exemplary embodiment of an implantableanchored sleeve including an eccentric eversion resistant feature and awave anchor;

FIG. 9 is cross-sectional schematic diagram of a portion of thegastrointestinal tract illustrating the location of the exemplaryimplantable sleeve of FIG. 8; and

FIG. 10 is cross-sectional schematic diagram of an exemplary embodimentof an implantable anchored sleeve including an eccentric eversionresistant feature.

DETAILED DESCRIPTION OF THE INVENTION

A description of preferred embodiments of the invention follows.

This invention relates to a method and device for implanting a sleevewithin a natural body lumen of an animal, the sleeve including ananti-eversion feature to inhibit eversion of the sleeve when implanted.In particular, the invention relates to a bypass sleeve adapted for usewithin the digestive tract of an animal. Some examples of suchintestinal implants are described in U.S. patent application Ser. No.11/000,099, filed Nov. 30, 2004, and entitled “Bariatric Sleeve”; U.S.patent application Ser. No. 11/001,794, filed Nov. 30, 2004, andentitled “Methods of Treatment Using a Bariatric Sleeve”; U.S. patentapplication Ser. No. 10/726,011, filed Dec. 2, 2003, and entitled“Anti-Obesity Devices”; U.S. patent application Ser. No. 10/810,317,filed Mar. 26, 2004, and entitled “Enzyme Sleeve”; and U.S. patentapplication Ser. No. 10/811,293, filed Mar. 26, 2004, and entitled“Anti-Obesity Devices” all incorporated herein by reference in theirentirety. As illustrated in FIG. 1A, an exemplary gastrointestinalsleeve 100 includes a sleeve anchor 105 coupled to the proximal end ofan elongated, thin-walled, floppy sleeve 110. The sleeve is hollow withopenings at both ends defining an interior lumen.

In this application, the sleeve is implanted within the intestine, suchthat chyme flowing within the intestine travels through the interior ofthe sleeve effectively bypassing that portion of the intestine.Preferably, the sleeve is thin-walled to so as to avoid irritating theintestine. Additionally, the thin-walled sleeve offers little resistanceto peristaltic forces. Exemplary wall thicknesses are between 0.0003 and0.0020 inches (i.e., 0.0076 and 0.051 mm).

Additionally, the sleeve material along the interior surface of thesleeve is smooth and slippery to avoid impeding the flow of chyme withinthe sleeve. Similarly, the exterior of the sleeve may also be smooth andslippery to promote the flow of material, such as digestive enzymes,between the exterior of the sleeve and the intestine wall. In someembodiments, the coefficient of friction of the sleeve material is about0.2 or less.

The sleeve anchor is adapted for removable attachment thereby securingat least a proximal portion of the sleeve to the intestine. Although thesleeve may be attached anywhere within the intestine, it is preferablyimplanted in the small intestine, distal to the pyloric sphincterbetween the pylorus and the ampulla of vater, with the attached sleeveextending distally into the intestine for a predetermined length. Anexample of such a device is described in U.S. patent application Ser.No. 10/858,851, filed on Jun. 1, 2004 and entitled “Intestinal Sleeve,”incorporated herein by reference in its entirety.

Although peristalsis provides a net resulting force directed antegradefrom the stomach, there are times in the digestion cycle during whichnegative pressures or reverse peristalsis may occur. These negative orretrograde pressures may be the result of natural mixing waves, or otherprocesses such as vomiting. The level of such pressures generated withinthe intestine are not well documented in the literature. Normalperistaltic pressures have been found to spike to 1.5-2.0pounds-per-square-inch gauge (PSIG) (i.e., about 41.5-55.4 inches H₂O).It is expected that reverse peristalsis could produce similar spikes inpressure. If the pylorus is open, even slightly during this rise inpressure, there exists a driving force to push a gastrointestinal liner(i.e., sleeve) retrograde towards the stomach. Experiments in a porcinemodel have resulted in occasional vomiting that resulted in sleevedevices anchored in the duodenum to evert both through and around theanchor into the stomach. Once everted, the sleeve no longer functionsand becomes obstructed.

The desirable features of being extremely thin-walled, floppy, andhaving a low friction coefficient all tend to make an intestinal sleevemore prone to eversion. At least two different eversion modes have beenobserved. A first eversion mode illustrated in FIG. 1B is referred to asa concentric eversion and is characterized by at least a portion of thesleeve 110 passing proximally through the center of the sleeve anchor105. A second eversion mode illustrated in FIG. 1C is referred to aseccentric eversion and is characterized by at least a portion of thesleeve 110 passing proximally between the exterior surface of the anchor105 and the interior surface (e.g., the tissue) of the body lumen withinwhich the device 100 is implanted.

Eversions of a sleeve are more prone to occur when there is a relativelystiff section (e.g., the anchor) followed by a flexible section. Thestiff section serves as a bending point or pivot for the flexiblematerial resulting in a natural stress concentration. The stiff sectionmust remain open during application of the pressure so the flexiblematerial has an opening through which to evert. The present inventionprevents such undesirable occurrences by providing a design feature thatinhibits the sleeves from everting.

Eversion resistance can be accomplished by providing an “eversionresistant” feature. For example, an eversion-resistant feature may beprovided at least at the transition between the anchor and the freesleeve as illustrated in FIG. 2A. As shown, a gastrointestinal implant200 includes a sleeve anchor 205 at its proximal end followed by anelongated sleeve 210 at its distal end. An eversion-resistant feature215 is provided at the transition between the anchor 205 and the sleeve210.

As retrograde force and/or pressure increases, the walls of theeversion-resistant feature 215 may experience a moment of force about apivot formed at the intersection of the relatively stiff anchor 205 andthe more flexible eversion-resistant feature 215 (i.e., there is atendency for the device to fold in upon itself as shown in FIG. 1B).Depending upon the magnitude of the force, the moment may tend to causeat least a partial rotation of the wall of the eversion-resistantfeature 215. However, because the eversion-resistant feature 215 isadapted to resist eversion, rotation may be limited to substantiallyless than 90°. This initial bending phase is referred to herein as apre-eversion phase and is schematically illustrated as phase I in FIG.2B.

As the retrograde force and/or pressure increases, bending of theeversion-resistant feature may continue, approaching 90°, until at leastsome of the interior surfaces of the eversion-resistant feature comeinto contact with each other. When the interior of theeversion-resistant feature 215 collapses upon itself, it is referred toas a collapsed phase and is schematically illustrated as phase II. It isbelieved that the resulting structure formed by the at least partiallycollapsed sleeve provides enhanced eversion-resistance performance.Namely, a collapsed portion of the device gains additional reinforcementfrom the collapsed region due at least partially to rotated materialfrom one side of the device pushing against similarly rotated materialfrom another side. Thus, further rotation about the pivot of either sideis at least partially inhibited by the opposite sides pushing againsteach other. A similar process is relied upon in reed-type valvessometimes referred to as “duckbill valves.” Additionally, to the extentthe surface material provides any non-insubstantial frictionalcoefficient, the resulting frictional force caused by overlapping layersof the material will resist movement of the material against itselfand/or its surroundings, thereby inhibiting further eversion.

With an even greater retrograde force and/or pressure, bending of theeversion-resistant feature about the pivot may continue beyond 90°. Asshown, the collapsed eversion-resistant feature 215 may begin to advanceproximally into the interior aperture of the anchor 205. When anon-insignificant portion of the eversion-resistant feature 215 beginsto advance proximally into the interior of the anchor 205, it isreferred to as a partial-eversion phase and schematically illustrated asphase III. It is believed that the eversion-resistance performanceremains enhanced during this phase as at least a portion of the deviceremains collapsed upon itself Thus the reinforcing and/or frictionalforces described above remain active. Consequently, there remains only alimited length of the device between the region of the collapse 215 andthe pivot point, which limits partial eversion according to the lengthof this region. Of course, at sufficient forces and/or pressures, eventhe eversion-resistant feature will evert.

The eversion performance of a material can be characterized by itseversion pressure, which is the pressure required to evert a tube formedfrom the raw material. The eversion pressure is a measure of severalproperties of the material being affected at least by the material'sstiffness and friction coefficient. Namely, raising either or both of amaterial's stiffness and friction coefficient yields higher materialeversion pressures. Material stiffness is a function of at least theflexural modulus or hardness of the material and its wall thickness. Thefriction coefficient is also relevant because as the eversion starts,the material tends to roll at least partially upon itself Once thematerial overlaps in this manner, any further movement requires that thematerial slide against itself Thus, higher friction coefficientmaterials tend to increase frictional forces encountered by an evertedsleeve, requiring increased forces to evert the materials once they havefolded upon themselves.

The eversion-resistant feature may include one or more of the followingattributes: increased stiffness or column strength, and an increasedfriction coefficient. An increased column strength resists that portionof the device 200 folding upon itself. Preferably, the length of thisregion ‘L’ is selected to allow at least a portion of the material tocollapse fully on itself when a backpressure is applied. It is believedthat such a collapse of the material forms a valve that can resist thepressure when the material is sufficiently stiff. The stiffness of thematerial is selected to promote its collapse and the formation of avalve at pressures at or near the eversion pressure of the otherwiseunmodified raw sleeve material. To enable collapse upon itself, thelength of the eversion-resistant feature 215 is greater than half thediameter of the internal lumen of the anchor 205 (i.e., L>D/2). Ideally,the eversion-resistant feature 215 also promotes collapse of the sleevetowards the elongated sleeve's central axis to prevent eccentriceversions.

One means of increasing the stiffness along the length of theeversion-resistant section 215 is to increase the material thickness.Increasing the thickness can be accomplished by layering the sleevematerial upon itself until the desired thickness is attained. In someembodiments, the sleeve-anchoring device is encapsulated within twolayers of sleeve material. Simply extending the region of the overlap apredetermined distance beyond the anchor itself provides a nice means ofcombining such functions. Alternatively, the eversion-resistant feature215 can be formed using a second material having a higher modulus,thereby creating a relatively stiffer section.

Yet another means of increasing the material stiffness is providingreinforcing members coupled to the eversion-resistant section. Forexample, stiffness is increased by coupling one or more soft guidewiresto the sleeve 210. At least one way to couple reinforcing members is toencase them within inner and outer layers of the sleeve material. Suchan approach reduces the possibility that the reinforcing member willentrap chyme, impede peristalsis, and irritate the surrounding tissue.The guidewire provides linear stiffness thereby resisting buckling,while still allowing the section 215 to collapse and also providinglittle resistance to peristalsis. The guidewire is preferably orientedparallel to the central axis of the sleeve. The wire could be a vasculartype guidewire commonly used to deliver catheters. These are typicallyconstructed from stainless steel coils and having diameters betweenabout 0.010 and 0.016 (i.e., 0.25 and 0.41 mm).

Materials such as soft, sticky silicone or polyurethane may be used inthe anti-eversion feature 215. In some embodiments, one or moreless-slippery materials are provided as a coating to the sleevematerial. Alternatively or in addition, the friction coefficient of theeversion-resistant feature is increased by including a textured surface.Similarly, as the textured material collapses upon itself and attemptsto roll inside out, the textured surface rubs against an adjacentsurface to resist further sliding of the materials.

An exemplary embodiment of an implant device includes a sleeve formedfrom an ePTFE/FEP bi-laminate material available from W. L. Gore &Associates Medical Products Division, Flagstaff, Ariz. The sleeve isformed having an internal diameter of about 1 inch (i.e., about 25 mm)with an unmodified eversion pressure of about 3-7 inches H₂O. For thepurposes of the testing, the length L of the eversion-resistant featureof the device was about 1.25 inches (i.e., about 3.2 cm) long.Additionally, the eversion-resistant feature was linearly tapered alongits length from about 50 mm to about 25 mm in diameter. The number oflayers of material used was varied from 2 covering the anchor, to 2 atthe transition from the anchor to the tube, to 3 in the tube section.Each layer of material was about 0.0004 inches (i.e., about 0.0102 mm)thick. This construction resulted in an eversion pressure of the strainrelief section of at least 30 inches H₂O but preferably 40-60 inchesH₂O. Preferably, transition from the anchor to the sleeve isaccomplished in a gradual manner. For example, the transition includesstaggering the thickness changes.

In some embodiments, the thickness of the eversion-resistant section is0.002-0.004 inches (i.e., about 0.051 to 0.102 mm) and requires about4-8 layers of the base material. This construction results in aneversion pressure of the strain relief section of at least 30 inchesH₂O. Devices have been made with pressures of 60 inches H₂O. The targetspecification is preferably between about 35-55 inches H₂O.

Animal testing in a porcine model has demonstrated that using a devicehaving a concentric eversion pressure of 30-60 inches H₂O, eliminatedthe occurrence of concentric eversions. However, a new failure mode wasobserved during testing, which is referred to as eccentric eversion.Several attributes of the test devices appeared to contribute to theeccentric eversions.

The transition region became substantially stiffer as more layers ofmaterial were applied. Also, the surface area of the anchor increased asthe relaxed diameter increased from 50 mm to 60 mm. This increases theeffective force acting on the anchor legs due to the pressure within theduodenum. With sufficient forces, one or more of the anchor legs can bepushed away from the wall of the duodenum. With the anchor deformed inthis manner, the relatively stiff reinforced sleeve section may bend inthe direction of the pressure towards the opening formed by the movedanchor leg. Thus, the net result of increasing the stiffness of thetransition region too much for a given stiffness of the anchor can leadto an increased susceptibility to eccentric eversions.

Susceptibility to eccentric eversion can be improved by decreasing therelative stiffness of the transition region while maintaining theincreased relative stiffness of the proximal sleeve. For example,stiffness of the transition was decreased by providing only 2 layers ofthe sleeve material; whereas, the relative stiffness of the first 1-2inches of the 25 mm tube was increased by adding 3 layers of the samematerial in that region. Beneficially, the resulting eversion pressureremains between about 30 and 60 inches H₂O while the likelihood ofeccentric eversions is substantially reduced. Also, the softertransition region promotes collapse of the region concentrically,thereby preventing it from falling towards a side potentially leading toan eccentric eversion.

Thus, an eversion resistant section is formed as a compound elementconsisting of at least two sections. The first can be a tapered sectionthat transitions from the 50 mm anchor to the 25 mm sleeve. This sectionserves several purposes. First, it makes the transition in diameters.Additionally, it serves as a so-called low-pressure “crumple zone.” Inother words, it collapses concentrically at low pressure without pullingthe anchor away from the tissue surfaces. Preferably, the length of thecrumple zone is no longer than the length of the anchor to avoid thecrumple zone everting through the anchor. In some embodiments, thelength of the crumple zone is about half the diameter of the sleeve.Then the second section is the stiffened sleeve section, which is drawntowards the center of the lumen by the collapse of the crumple zone.This area is stiff and therefore resists concentric eversion. Thissection may be tapered from 3 layers to 1.

Measurement of concentric eversion-threshold pressure can be performedusing a water-based test configuration measuring directly the inches ofH₂O required to evert the device. As shown in FIG. 3A, the anchor 305 ofa 25 mm diameter device is sealably attached to the interior of a 25 mmdiameter silicone tube 320. The attached sleeve 310′ is tied off at somedistance from the anchor 305 (e.g., about 6 inches from the anchor). Theclosed sleeve is extended within the tube 320 distal to the anchor 305.The tube 320 is bent into a ‘U’ shape with the device being placed inone of the vertical legs with other vertical leg being left open.

In operation, the tube 320 is partially filled with water from its openend. The water in the tube 320 represents a column of water applied tothe distal side of the anchor 305. The open end of the tube is thenraised with respect to the device, such that the potential energy of thedisplaced water provides a retrograde pressure upon the sleeve 310′. Atsome height, the sleeve 310″ everts through the anchor 305 as shown inphantom. The corresponding height of the water at which the sleeve 310″everted is recorded as the corresponding eversion pressure in inchesH₂O.

Another method of measuring concentric eversion-threshold pressure usesair rather than water. Air is preferred as it does not contaminate thetested materials, such that they can then be later used for implant.This set up is used to test the eversion pressure of either the rawmaterial or the finished device. Raw material may be tested as anincoming quality assurance inspection to ensure consistency of thematerial. The overall concept described below is similar to thewater-based test configuration.

Referring to FIG. 3B, the anchor 305 of a 25 mm diameter device issealably attached to the interior of a 25 mm diameter silicone tube 380.The attached sleeve 310′ is tied off at some distance from the anchor305 (e.g., 6 inches from the anchor). The closed sleeve 310′ is thenextended within the tube 380 distal to the anchor 305. Air is suppliedto the bottom of the tube 380 from a regulated air supply 355, such as aregulated air compressor through a flow-control system. The output ofthe air supply 355 is coupled through a needle valve 360 to one end of aflow meter 365. The other end of the flow meter 365 is coupled to oneend of a check valve 370. The other end of the check valve is coupled toone end of the tube 380. A pressure-measuring device, such as amanometer 375 is coupled between the check valve 370 and the tube 380 tomeasure the pressure applied to the tube.

In operation, the check valve 370 is closed while a device under test isinserted into the tube 380. The device under test may be either samplesof raw sleeve material or finished implants including eversion-resistantfeatures. The needle valve 360 may be set to a pre-established flow ratesuch that the pressure will rise within the tube at a desired rate(i.e., not too fast to allow an operator to record pressure readingsfrom the manometer 375. The check valve 370 is opened applying airpressure to the tube 380. As the pressure increases above theeversion-threshold pressure, the sleeve 310″ will evert through thecenter of the anchor 305 as shown in phantom. The corresponding maximumpressure at which the sleeve everted is recorded as the correspondingeversion pressure.

Either test configuration may be used to measure corresponding eversionpressures of devices with or without eversion-resistant features. Thus,comparative results between the two measurements provides a performancemeasure of any improvement provided by the eversion-resistant feature.

In some embodiments as shown in FIG. 4A, an implant device 400 includesan anchor 405 defining an interior lumen having a first diameter D₁coupled to a sleeve 410 defines an interior lumen having a seconddiameter D₂. For example, the anchor includes a first diameter that isgreater than the sleeve's diameter (i.e., D₁>D₂). This configuration isadvantageous at least in gastrointestinal applications in which a sealbetween the anchor and the body lumen is desired. Thus, the anchor 405functions in part as a radial spring, providing an outward force againstthe surrounding tissue when implanted. In order to provide the outwardforce, the resting diameter of the anchor is larger than the diameterwhen implanted.

A tapered eversion-resistant feature 415 can be applied between theanchor 405 and the sleeve 410, the feature 415 providing a transitionfrom one diameter to another. For example, the eversion-resistantfeature 415 is an open cone transitioning from D₁ to D₂. Theeversion-resistant feature 415 can include any of the propertiesdescribed above including increased stiffness and/or frictioncoefficient. Similarly, these properties can be applied using any of thetechniques described herein, the main difference being the tapered shapeof the resulting treated area.

FIG. 4B illustrates deformation of the eversion-resistant feature 415when subjected to retrograde pressures. Preferably, theeversion-resistant feature 415 collapses upon itself whereby thematerial properties resist eversion thereby blocking any opening throughwhich the distal sleeve 410 may evert.

In some embodiments, an eversion-resistant feature is provided as acompound element providing different properties along different portionsof the treated surface area. As shown in FIGS. 5A and 5B, an implantdevice 500 includes a proximal anchor 505 and a distal sleeve 510. Theeversion-resistant feature provided between the anchor 505 and thesleeve 510 is applied resulting in at least two distinguishable regions.A proximal region 515 extends distally for a first length L₁ from thedistal end of the anchor 505. A distal region 520 extends distally fromthe first region 515 for a second length L₂. The raw sleeve materialextends distally from the distal end of the second region.

Such a compound eversion-resistant feature can provideeversion-resistance to both concentric eversions and to eccentriceversions. For example, the proximal region 515 can be configured as aso-called “crumple zone.” As the name suggests, when subjected tosufficient retrograde pressures, the proximal region 515 collapses uponitself as described above in reference to FIGS. 2 and 4. The distalregion 520 can be configured as a so-called reinforced region having ahigher eversion-resistance than the proximal region 515 to resistcrumpling at the same pressure. The initial collapse of the proximalregion 515 tends to center the distal region 520, such that furthercollapse of that region occurs towards the center rather than along theedge as the retrograde pressure continues to increase. Collapse of thedistal region 520 ultimately blocks the central lumen without evertingfully, thereby prohibiting further eversion of the sleeve 510 throughthe blocked lumen.

A tapered device having a compound eversion-resistant feature isillustrated in FIGS. 6A and 6B. The device 600 includes a proximalanchor having a first diameter D₁ (e.g., about 50 mm) coupled through aneversion-resistant feature to the proximal end of an elongated sleevehaving a second diameter D₂ (e.g., about 25 mm). Typically, the sleeve'sdiameter is less than that of the anchor 605 (i.e., D₁>D₂). The compoundeversion-resistant feature includes a proximal region 615 extending fora first length L₁ (e.g., about 1.5 inches) followed by a distal region620 extending for a second length L₂ (e.g., about 1.0 inch).

The proximal region 615 can be configured as a crumple zone and thedistal region 620 can be configured as a reinforced region. In thepresence of sufficient retrograde pressures, the proximal region 615collapses upon itself first while the distal region remainssubstantially open. As the pressure continues to increase, the distalregion 620 also collapses upon itself, being substantially centered bythe initially-collapsed crumple zone 615, thereby avoiding an eccentriceversion.

In some embodiments, tapering from the first D₁ to D₂ is accomplished inthe proximal region 615. It is believed that applying a taper to thisregion may further enhance performance of the eversion-resistant featureby focusing collapse of the material towards the device's longitudinalaxis.

Measurement of eccentric eversion susceptibility can be accomplishedusing an eccentric-measurement test setup. An exemplary test setup isillustrated in FIGS. 7A and 7B. The anchor of an implant device undertest is coupled to the interior of a large-diameter silicon tube (e.g.,about 40 mm for a 50 mm diameter anchor). A weight is then attached to adistal end of the sleeve at a predetermined distance from the anchor.The weight is raised above the anchor to fully extend the sleeve. Forexample, the weight can be a metal rod that is placed inside the sleeve,coupled to the sleeve, and dropped from a height of about 6 inches(i.e., about 15 cm) towards the anchor. The metal rod is relativelynarrow. For example, a metal rod about 0.5 inches (i.e., about 13 mm) indiameter that weighs about 0.6 pounds (i.e., 0.23 kg) was used for testresults provided herein.

The weight is dropped towards the anchor and depending upon the deviceunder test, the weight may travel through the center of the anchorresulting in a concentric eversion, or the weight may travel towards aside of the anchor resulting in an eccentric eversion. The test isrepeated a predetermined number of times for the same device under test.Eccentric eversion susceptibility is determined as the percentage oftotal tries resulting in an eccentric eversion.

Thus, this test can be used to measure the eccentric eversionsusceptibility of different devices and is useful in identifyingfeatures that reduce or eliminate the eccentric eversion failure mode.Four different devices were tested using the test configuration of FIGS.7A and 7B. The devices are described in Table 1.

TABLE 1 Devices Under Test Design Eversion Material Layering # Anchordesign design thickness method 1 60 mm OD × Single cone 0.0010″- Wrapped0.020″ wire transition 0.0015″ diameter element and short cylinder 2 50mm OD × Single cone 0.0015″- Template 0.023″ wire transition 0.0020″diameter element 3 50 mm OD × Single cone 0.0010″- Wrapped 0.023″ wiretransition 0.0015″ diameter element and short cylinder 4 50 mm OD ×Single cone Cone is 2 Template 0.023″ wire transition layers (0.0010″)diameter (most element and Cylinder is 3 recent design) long cylinderlayers (0.0015″)

Exemplary data resulting from 30 attempts per device for each of the 4different devices is summarized in Table 2.

TABLE 2 Eccentric Test Results Device Concentric Eccentric % EccentricDesign 1 20 10 33.3%   Design 2 13 2 13.3%*   Design 3 30 0 0% Design 430 0 0% *15 tries only - device broke

These tests showed that the eversion-resistant features of devices 3 and4 are much less susceptible to the eccentric-eversion failure mode.These data also are supported by animal evaluations. Designs 1 and 2 hadhigh rates of eccentric eversion in pigs. Design 3 was an early designin which eversions were very rare. Design 4 has also resulted in adevice in which eversions are rare in animal testing.

An embodiment combining a wave anchor with a compound eversion-resistantfeature is illustrated in FIG. 8. The device is similar to thatdescribed above in reference to FIG. 6A in that it includes a proximalanchor 705 having a first diameter and a distal elongated sleeve 710having a second diameter less than the first. A compoundeversion-resistant feature includes a proximal region 715 adjacent tothe anchor and tapered between the first and second diameters. Areinforced region 720 is provided between the proximal region 715 andthe proximal sleeve 710. The anchor 705, however, is illustrated in moredetail. In particular, the anchor can be a wave anchor defining multipleoscillations about a central lumen as described in U.S. application Ser.No. 10/858,852, filed on Jun. 1, 2004, and entitled “Method andApparatus for Anchoring Within the Gastrointestinal Tract” incorporatedherein by reference in its entirety. As shown, the proximal portion ofthe sleeve can be tailored to the boundary defined by the anchorresulting in the tulip-petal shape. The anchor, when implanted isreduced in diameter slightly by the local anatomy of the body lumen.Beneficially, the outward radial spring force provided by thepartially-compressed anchor results in a sealable connection between theproximal end of the device and the interior surface of the body lumen.

The spring force of the anchor provides some anchoring force to maintainthe anchor in a predetermined location. However, the anchor can beattached to the local anatomy using one or more external connectingmeans. For example, the anchor can be sutured in place, coupled usingsurgical staples, and/or coupled using surgical adhesives. Preferably,the anchor is attached to the anatomy in a removable fashion. Forexample, the anchor can optionally include one or more barbs 725 orspines protruding outward and adapted to engage the surrounding musculartissue.

Alternatively or in addition, the device can include one or morefeatures adapted to facilitate removal of the device. For example, thedevice can include one or more drawstrings 730 at its proximal end. Thedrawstrings are slideably attached to the proximal ends of the anchorand are adapted to centrally collapse the anchor when suitably engaged.Preferably, the collapse pulls any barbs out of the surrounding tissueprior to removal to avoid unnecessary tissue damage. A separate removaldevice can then be used to remove the device as described in pendingU.S. Provisional Application No. 60/663,352, filed on Mar. 17, 2005, andentitled “Removal and Repositioning Devices,” incorporated herein byreference in its entirety.

FIG. 9 shows a cross-sectional view of a portion of a duodenum 750 witha device implanted therein. The anchor 705 is situated in the proximalduodenum in an area referred to as the bulbous duodenum 765, locateddistal to the pyloric sphincter 755 and proximal to the ampulla of vater760. The anchor 705 is partially compressed resulting in a fluid sealbetween it and the surrounding intestine wall. The sleeve 710 extendsdistally into the duodenum 750 and, depending upon its length, beyondthe duodenum into distal parts of the small intestine not shown.

FIG. 10 shows a cross section of one embodiment of the sleeve 700 shownin FIG. 9 using overlapping material to form the different regions ofthe compound eversion feature. Starting at the proximal end, a waveanchor 705 is surrounded by an inner and outer layer of the sleevematerial. The proximal anti-eversion region 715, or tapered crumplezone, is similarly formed using two layers of the same sleeve material.Preferably, some amount of overlap O₁ is provided to facilitateattachment of the covered anchor 705 to the proximal end of the crumplezone 715. For example, the two regions may be attached using anadhesive. Alternatively or in addition, the two regions may be attachedusing a mechanical fastener such as a suture. Preferably, however,thermal boding is used to sealably connect the two regions togetheralong the periphery of the device within the overlapping region O₁.

A proximal end of the sleeve similarly overlaps a distal end of thecrumple zone by a length O₂ to facilitate attachment of the two regions.Any of the above means of attaching can be used to form the attachment.A second and third layers are added just distal to the end of thecrumple zone 715, thereby forming a reinforced region 720 having threelayers of sleeve material. As shown, the outer-most layer 725 of thereinforcing region 720 may extend beyond the second layer 727 and attachto the outer surface of the sleeve 710 to form a smooth transition.

Although a gastrointestinal sleeve is described as an exemplaryembodiment, other applications include arterial grafts, esophagealprostheses, and other gastrointestinal prostheses, such as biliarysleeves.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

1. A device for implanting within a lumen having a longitudinal axis, the sleeve comprising: an anchor adapted for attachment with the lumen; a sleeve coupled to a distal end of the anchor and adapted for extension within a gastrointestinal tract, the sleeve including: a crumple zone coupled to the distal end of the anchor and having walls of the sleeve adapted to collapse concentrically upon themselves in the presence of retrograde pressure; a reinforced zone coupled to a distal end of the crumple zone, the reinforced zone having walls stiffer than the walls of the crumple zone; and a thin-walled zone extending from a distal end of the reinforced zone to a distal end of the device, the thin-walled zone being prone to eversion in the presence of retrograde pressure.
 2. The device of claim 1 wherein, when in a relaxed state, the anchor has a diameter of at least about 40 mm.
 3. The device of claim 1 wherein, when collapsed concentrically, the crumple zone forms a valve that allows flow in an antegrade direction and inhibits flow in a retrograde direction.
 4. The device of claim 1 wherein the crumple zone tapers from a first diameter at a proximal opening to a second diameter at a distal opening, the first diameter being larger than the second diameter.
 5. The device of claim 4 wherein the distal opening of the crumple zone is coupled to a proximal opening of the reinforced zone.
 6. The device of claim 4 wherein the first diameter is about 50 mm or more and the second diameter is about 25 mm.
 7. The device of claim 1 wherein the crumple zone has a length of about 1.5 inches and the reinforced zone has a length of about 1.0 inch.
 8. The device of claim 1 wherein a surface of the reinforced zone has a coefficient of friction greater than that of a corresponding surface of the thin-walled zone.
 9. The device of claim 1 wherein the walls of the reinforced zone have a thickness within a range of between about 0.0008 inch and about 0.0040 inch.
 10. The device of claim 1 wherein walls of the thin-walled zone have a thickness of about 0.0005 inch.
 11. The device of claim 1 wherein the device is configured to provide a concentric eversion pressure of at least 30 inches H₂O.
 12. A device for implanting within an animal body comprising: an anchor adapted for attachment within a gastrointestinal tract; a sleeve coupled to a distal end of the anchor and adapted for extension within the gastrointestinal tract, the sleeve including: an eversion-resistant feature coupled to a distal end of the anchor, the eversion-resistant feature being a taper of the sleeve from a first diameter at a proximal opening to a second diameter at a distal opening, the first diameter being larger than the second diameter, at least part of the eversion-resistant feature being configured to collapse concentrically upon itself in the presence of retrograde pressure; and a thin-walled zone coupled to the distal opening of the eversion-resistant feature, the thin-walled zone being adapted for extension into the gastrointestinal tract and prone to eversion in the presence of retrograde pressure.
 13. The device of claim 12 wherein the first diameter is about 50 mm or more and the second diameter is about 25 mm.
 14. The device of claim 12 wherein, when in a concentrically collapsed state, the eversion-resistant feature forms a valve that allows flow in an antegrade direction and inhibits flow in a retrograde direction.
 15. A device for implanting within a lumen having a longitudinal axis, the sleeve comprising: an anchor adapted for attachment within a gastrointestinal tract; and a sleeve adapted for extension into the gastrointestinal tract, the sleeve comprising: a thin-walled zone configured to be deployed within a gastrointestinal tract, the thin-walled zone being prone to eversion in the presence of retrograde pressure; and a tapered segment of the sleeve disposed between a proximal end of the thin-walled zone and a distal end of the anchor, the tapered segment of the sleeve collapsing concentrically upon itself in the presence of retrograde pressure.
 16. The device of claim 15 wherein the thin-walled zone extends to a distal end of the device.
 17. The device of claim 15 wherein walls of the thin-walled zone have a thickness of about 0.0005 inch.
 18. The device of claim 15 wherein, when collapsed from a first diameter to a second diameter, the tapered segment forms a valve that allows flow in an antegrade direction and inhibits flow in a retrograde direction.
 19. The device of claim 15 wherein the tapered segment has a proximal opening with a diameter of about 50 mm or more and a distal opening with a diameter of about 25 mm. 